The invention relates to a method for coating the balloon of a balloon catheter, wherein the surface of the balloon is wetted at least partially with a first solution of an active agent and said part of the surface of the balloon wetted with said first solution of an active agent is wetted with a liquid containing water and/or at least one alcohol. Moreover, the invention relates to the balloon and the balloon catheter itself.
In medicine, so-called “minimally invasive procedures” play an ever increasing role. Percutaneous transluminal angioplasty (PTA) by means of balloon dilatation is frequently employed for the treatment of vasoconstrictions such as arteriosclerosis. For this purpose, a balloon catheter provided in its distal area with a balloon inflatable by the infeed of a fluid is brought to the stenotic site (vasoconstriction) with the help of a guide catheter. At the stenotic site the balloon is inflated causing deposits/plaque inhibiting the flow of blood to be pressed against or into the vessel wall so that unhindered perfusion is restored. To rule out the reoccurrence of such a vessel constriction a stent may often be implanted to keep the vessel open. After collapsing of the balloon the balloon catheter is withdrawn and removed from the vascular system whereas a stent that may have been implanted will remain in the vessel.
Within the framework of angioplasty the vessel, however, may again suffer constriction (restenosis) after the balloon catheter has been removed, which is due to the proliferation of cells, i.e. cells grow into the vessel lumen and again impede the free flow of blood. To prevent this undesirable effect, balloon catheters coated with medical substances are employed, which enables such a substance to be applied to the inner wall of the vessel at the location where stenosis has occurred, with said medical substance usually having a proliferation-inhibiting effect that shall prevent restenosis.
Typically, an active substance dissolved in a solvent is applied to the surface of the balloon, with the solvent subsequently evaporating. The active agent is present in the form of a layer on the surface and can be applied while balloon dilatation takes place. In this context, adherence of the active agent on the balloon has turned out to be problematic.
In publications U.S. Pat. No. 5,102,402 and U.S. Pat. No. 6,129,705 for example it has been described how the adherence of an active agent on the surface can be improved. Publication U.S. Pat. No. 5,102,402 provides elucidation of a balloon catheter coated with medical substances. In a first variant thereof microcapsules filled with an active agent or drug are enclosed in folds in the balloon surface and in this way are mechanically retained in their relevant positions. In a second variant the microcapsules are attached to the balloon surface with the aid of an adhesive.
In publication U.S. Pat. No. 6,129,705 a balloon catheter has been described the surface of which is provided with a coating into which the microcapsules filled with an active agent are completely embedded. It is to be noted, however, that filling the active agent into microcapsules and subsequently attaching the microcapsules to or embedding them in the surface of the balloon are comparatively sophisticated and thus expensive processes.
In principle, it is desirable for the surface of the balloon of the balloon catheter to be provided with a homogenous and reproducible load of medical substances and also release the drugs to the surrounding tissue in the body in a uniform manner.
As per a method explained in detail in WO 2010/009904 A2 the surface of the balloon shall initially be treated with a first solution of the active agent and subsequently treated with a second solution of the same active agent. In this way, a more brittle, chalk-like surface is created that results in an improved release of the active agent when the balloon is pressed against the inner wall of the vessel to be treated, as compared with surface coatings produced through a treatment with only a first solution.
In the past, problems were encountered, however, in that a significant amount of the active agent was carried away by the blood stream either at the time the balloon catheter was inserted into the blood vessel or within a relatively short period thereafter and thus was no longer available to fulfill the intended purpose. After the balloon catheter has been removed the release of the active agent diminishes very quickly.
It is therefore the object of the invention to provide a method for coating the balloon of a balloon catheter, respectively a balloon/balloon catheter, by means of which an improved long-term effect can be achieved.